Laserverfahren in der Umweltanalytik

Panne, Ulrich; Nießner, Reinhard

doi:10.1007/978-3-642-60643-4_4

“…Here, the limits of detection can be improved considerably [82] if fluorescence is excited by a laser (LIF). This is very important for the measurement of polycyclic aromatic hydrocarbons [170]. A survey on fluorescence spectroscopy in biology has been published [171].…”

Section: Applicationsmentioning

confidence: 99%

Ultraviolet and Visible Spectroscopy

Gauglitz

¹

2008

Ullmann's Encyclopedia of Industrial Chemistry

0

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The article contains sections titled: 1. Introduction 1.1. Comparison with Other Spectroscopic Methods 1.2. Development and Uses 2. Theoretical Principles 2.1. Electronic States and Orbitals 2.2. Interaction Between Radiation and Matter 2.2.1. Dispersion 2.2.2. Absorption 2.2.3. Scattering 2.2.4. Reflection 2.2.5. Band Intensity 2.3. The Lambert–BeerLaw 2.3.1. Definitions 2.3.2. Deviations from the Lambert ‐ Beer Law 2.4. Photophysics 2.4.1. Energy Level Diagram 2.4.2. Deactivation Processes 2.4.3. Transition Probability and Fine Structure of the Bands 2.5. Chromophores 2.6. Optical Rotatory Dispersion and Circular Dichroism 2.6.1. Generation of Polarized Radiation 2.6.2. Interaction with Polarized Radiation 2.6.3. Optical Rotatory Dispersion 2.6.4. Circular Dichroism and the Cotton Effect 2.6.5. Magnetooptical Effects 3. Optical Components and Spectrometers 3.1. Principles of Spectrometer Construction 3.1.1. Sequential Measurement of Absorption 3.1.2. Multiplex Methods in Absorption Spectroscopy 3.2. Light Sources 3.2.1. Line Sources 3.2.2. Sources of Continuous Radiation 3.2.3. Lasers 3.3. Selection of Wavelengths 3.3.1. Prism Monochromators 3.3.2. Grating Monochromators 3.3.3. Electro‐Acoustic and Opto‐Acoustic Wavelength Generation 3.4. Polarizers and Analyzers 3.5. Sample Compartments and Cells 3.5.1. Closed Compartments 3.5.2. Modular Arrangements 3.5.3. Open Compartments 3.6. Detectors 3.7. Optical Paths for Special Measuring Requirements 3.7.1. Fluorescence Measurement 3.7.2. Measuring Equipment for Polarimetry, ORD, and CD 3.7.3. Reflection Measurement 3.7.4. Ellipsometry 3.8. Effect of Equipment Parameters 3.9. Connection to Electronic Systems and Computers 4. Uses of UV ‐ VIS Spectroscopy in Absorption, Fluorescence, and Reflection 4.1. Identification of Substances and Determination of Structures 4.2. Quantitative Analysis 4.2.1. Determination of Concentration by Calibration Curves 4.2.2. Classical Multicomponent Analysis 4.2.3. Multivariate Data Analysis 4.2.4. Use in Chromatography 4.3. Fluorimetry 4.3.1. Inner Filter Effects 4.3.2. Fluorescene and Scattering 4.3.3. Excitation Spectra 4.3.4. Applications 4.4. Reflectometry 4.4.1. Diffuse Reflection 4.4.2. Color Measurement 4.4.3. Regular Reflection 4.4.4. Determination of Film Thickness 4.4.5. Ellipsometry 4.5. Resonance Methods 4.5.1. SurfacePlasmon Resonance 4.5.2. Grating Couplers 4.5.3. Other Evanescent Methods 4.5.4. Interferometric Methods 4.6. On‐Line Process Control 4.6.1. Process Analysis 4.6.2. Measurement of Film Thicknesses 4.6.3. Optical Sensors 4.7. Measuring Methods Based on Deviations from the Lambert – Beer Law 5. Special Methods 5.1. Derivative Spectroscopy 5.2. Dual‐Wavelength Spectroscopy 5.3. Scattering 5.3.1. Turbidimetry 5.3.2. Nephelometry 5.3.3. Photon Correlation Spectroscopy 5.4. Luminescence, Excitation, and Depolarization Spectroscopy, and Measurement of Lifetimes 5.5. Polarimetry 5.5.1. Sugar Analysis 5.5.2. Cellulose Determination 5.5.3. Stereochemical StructuralAnalysis 5.5.4. Use of Optical Activity Induced by a Magnetic Field 5.6. Photoacoustic Spectroscopy (PAS)

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“…B. von Reaktorgut in der chemischen Technologie oder Biotechnologie [1][2][3], in den Umweltwissenschaften [4] oder zur In-vivo-Analytik in der Biomedizin [5; 6] erleben in jüngs-ter Zeit enorme Aufmerksamkeit in Industrie und Wissenschaft. Vor allem die nicht-invasive Betriebsweise und die Verwendbarkeit von Lichtwellenleitern, die unempfindlich gegenüber äußeren elektromagnetischen Störfeldern das detektierte Lichtsignal zu einer zentralen Auswerteeinheit übertragen können, machen die optischen Techniken attraktiv.…”

Section: Introductionunclassified

In-situ-Analytik heterogener Medien mit frequenz- und leistungsmodulierten Diodenlasern (In-situ Analysis of Heterogeneous Media with Frequency and Intensity Modulated Diode Lasers)

Schael¹,

Reich²

2001

Teme

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Die elektronische Leistungs-und Frequenzmodulierbarkeit von Diodenlasern eröffnet neue Perspektiven für eine Reihe von hochempfindlichen In-situ-Analyseverfahren. Besonders für ,,heterogene" Medien aus den Bereichen der chemischen Technologie, Biotechnologie und Biomedizin, die häufig Gas-, Flüssig-und Festphase nebeneinander enthalten und starke Lichtstreuung aufweisen, ergeben sich nicht-invasive und z. T. konkurrenzlose Analysetechniken. Mit leistungsmodulierten Lasern können in den Proben Photonendichtewellen ausgelöst werden, deren Detektion und Auswertung u. a. einen nicht-invasiven Zugang zu Absorptionsund Streukoeffizient eröffnet. Der Absorptionskoeffizient gestattet qualitative und quantitative Bestimmung von Inhaltsstoffen. Der Streukoeffizient ermöglicht eine physikalische und morphologische Charakterisierung. Die vorliegende Arbeit zeigt die Anwendbarkeit entsprechender Theorien anhand von einfachen Modelllösungen und ermöglicht einen Vergleich mit Auswertungen nach der Theorie von Kubelka und Munk. Messungen von Humanblutproben werden diskutiert. Ein neues Verfahren zur Bestimmung von Porenfeuchte in Schäumen mit einem frequenzmodulierten Diodenlaser in externer Kavität wird demonstriert.Electronic intensity and frequency modulation of diode lasers enables new perspectives for highly sensitive analytical in-situ techniques. For analysis of ,,heterogeneous" media, which may consist of coexisting gaseous, liquid, and solid phases and often show multiple light scattering, non-invasive techniques with outstanding performance characteristics can be developed. Analysis of photon density waves launched by intensity-modulated lasers provide an elegant way for the determination of absorption and scattering coefficients of multiple scattering media. The absorption coefficient can be used for qualitative and quantitative analysis of chemical constituents (which absorb in the range of the laser wavelengths). The scattering coefficient allows characterization of physical and morphological properties of the sample. In the current work, applicability of appropriate radiation transport models was investigated with simple light scattering solutions and compared with results obtained from the treatment according to the theory of Kubelka and Munk. Measurements of human blood samples are discussed. A new method for determination of water vapor partial pressure in a polyurethane foam with a frequency-modulated external cavity diode laser is demonstrated. Schlagwörter: Diodenlaser, Modulationsspektroskopie, Photonendichtewellen 448 tm -Technisches Messen 68 (2001) 10  Oldenbourg Verlag

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